Primitive snake had legs

NEW YORK - A fossil find in Argentina has revealed a two-legged creature that's the most primitive snake known, a discovery that promises to fire up the scientific debate about whether snakes evolved on land or in the sea.

The snake's anatomy and the location of the fossil show it lived on land, researchers said, adding evidence to the argument that snakes evolved on land.

Snakes are thought to have evolved from four-legged lizards, losing their legs over time. But scientists have long debated whether those ancestral lizards were land-based or marine creatures.

The newly found snake, named Najash rionegrina, lived in Patagonia. Its exact size is unknown, but it wasn't more than 3 feet long, said Hussam Zaher of the University of Sao Paulo in Brazil, reporting his findings in Nature.

It's the first time scientists have found a snake with a sacrum, a bony feature supporting the pelvis, Zaher said. That feature was lost as snakes evolved from lizards, he said, and since this is the only known snake that hasn't lost it, it must be the most primitive known.

The creature clearly lived on land, both because its anatomy suggests it lived in burrows and because the deposits where the fossils were found came from a terrestrial environment, said Zaher. So, if the earliest known snake lived on land, that suggests snakes evolved on land, he said.

He said that although the creature had two small rear legs, it crawled like a modern-day snake and probably used its legs only on occasion.

The creature's "a fantastic animal," said Jack Conrad of the American Museum of Natural History in New York. "It's really going to help put to rest some of the controversy."

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